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A046237
Numbers whose cube is palindromic in base 7.
1
0, 1, 2, 4, 8, 16, 50, 100, 200, 344, 688, 1376, 2402, 4804, 9608, 16808, 33616, 67232, 117650, 235300, 470600, 823544, 1647088, 3294176, 5764802, 11529604, 23059208, 40353608, 80707216, 161414432, 282475250, 564950500, 1129901000, 1977326744, 3954653488, 7909306976
OFFSET
1,3
COMMENTS
Contains triples with base-7 digits 10^k1, 20^k2, 40^k4 for k >= 1, where ^ denotes repeated concatenation. - Michael S. Branicky, Aug 02 2022
LINKS
Patrick De Geest, World!Of Numbers, Palindromic cubes in bases 2 to 17.
PROG
(PARI) isok(k) = my(d=digits(k^3, 7)); Vecrev(d) == d; \\ Michel Marcus, Aug 02 2022
(Python)
from itertools import count, islice
from sympy.ntheory import is_palindromic as ispal
def agen(start=0): yield from (k for k in count(start) if ispal(k**3, 7))
print(list(islice(agen(), 22))) # Michael S. Branicky, Aug 02 2022
CROSSREFS
Cf. A046238.
Sequence in context: A027155 A129335 A264635 * A013084 A263535 A018681
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, May 15 1998
EXTENSIONS
a(30)-a(36) from Michael S. Branicky, Aug 03 2022
STATUS
approved